Using mammalian virus systems and combined electron microscopic and biochemical methods, in vivo intermediates in poliovirus translation have been detected and isolated, in vitro poliovirus RNA replication intermediates have been isolated and characterized, new early proteins of adenovirus have been localized, and high resolution molecular mapping of viral genomes has been performed. BIBLIOGRAPHIC REFERENCES: Chin, W.W. and Maizel, J.V.: The Polypeptides of Adenovirus. VIII. The Enrichment of E3 (11,000) in the Nuclear Matrix Fraction. Virology 76: 79-89, 1977. May, F., Maizel, J.V. and Salzmann, N.P.: Mapping of Transcription Sites of Simian Virus 40 - Specific Late 16S an 19S mRNA by Electron Microscopy. Proc. Natl. Acad. Sci. U.S.A. 74: 496-500, 1977.